Production of pure ductile vanadium from vanadium oxide



Patented July 24, 1951 a.

T FF! CE PRODUCTION OF PURE DUCTILE VANADIUIVI FROM VANADIUM OXIDE No Drawing. Application September 30', 1949,

Serial No. 119,012

3 Claims. (CI. 7584) 1 This invention relates to the manufacture of metallic vanadium and more particularly to the preparation of ductile vanadium in the form of massive bodies which can easily be worked into desired shapes because of their malleability.

The problem of preparing pure metallic vanadium has presented numerous difficulties. A large number of attempts have been made by various workers, using a variety of methods, but in general the results have been disappointing." The two preceding sentences have been quoted verbatim from page 6 of chapter 14 in Chapters in the Chemistry of the Less Familiar Elements by B. Smith Hopkins. Then after describing briefly a number of attempts to obtain metallic vanadium, Hopkins on page 7 says, This formidable array of serious efiforts and the mediocre results generally obtained makes it clear that the production of pure vanadium is a diiicult task.

The best previously known method of producing metallic vanadium, which was devised by Marden and Rich, involved the reduction of V205 with metallic calcium in a flux composed of calcium chloride. This method of producing vanadium suffers from the drawback that the metallic vanadium is obtained in the form of small particles which range in size from small pellets to fine dust. These small particles of vanadium must then be sintered and agglomerated in order to form a coherent body of vanadium that can be mechanically fabricated in accordance with conventional metal working methods. Applicants have found that due to rather low yields and dimculties in recovery the Marden and Rich method is of no value other than for a laboratory scale production of vanadium. Applicants thereby have confirmed Hopkins contention that"this method of production does not look promising from a commercial point of view. This invention has as an object the provision 'of a commercially feasible method of obtaining metallic vanadium. A further object is to provide a method of obtaining metallic vanadium in the form of a massive body which can be readily fabricated in accordance with conventional methods for working malleable metals. A still further object is to provide a method of manufacturing ductible vanadium in which the production of small metallic particles which must be sintered and agglomerated is very greatly reduced anda massive regulus of vanadium is obtained. Other objects will appear hereinafter.

These objects are accomplished accordance with the present invention by reacting a mixture containing vanadium pentoxide and at least 0.05

mol of iodine per mol of V205 with at least 40% more metallic calcium than is stoichiometrically needed to react with said vanadium pentoxide and iodine; and then separating the massive body of ductile vanadium thereby'obtained from the slag produced in the reaction.

This invention is illustrated but not limited by the following example:

Example An intimate mixture of 280 parts by weight of chemically pure V205 625 parts by weight of high purity calcium and '78 parts by weight of chemically pure iodine was made by tumbling in a closed container for about five minutes. This mixture was charged into a high fired, magnesia liner with a lid and the assembly loaded into a.

. steel bomb lined with about A inch of refractory sand. Refractory sand was poured over the closed liner, with about a inch layer on top. The bomb wassealed, the contents evacuated and filled three times with pure argon gas.

This assembly was placed in a high frequency field and heated eight minutes. The main reduction reactionwas noted at about seven minutes by a crackling noise within the bomb followed by the rapidheating of the bomb, a maxi mum temperature of about 737 C. being obtained. Next day the bomb was opened and examined. While some of the excess calcium had condensed on the walls of the bomb, it appeared that most of the excess calcium was mixed with the slag. The slag, which was principally CaO', looked fused near the top of the bomb and appeared as gold colored crystals near the bottom. It was found that a fairly well collected regulus of metallic vanadium had formed near the bottom of the bomb. This regulus accounted for about of the metallic vanadium that is theoretically obtainable in this reaction. The rest of the vanadium was in small shots or pellets. dispersed through the slag. The regulus was washed with water to free it from any adhering slag. The vanadium regulus produced in this way was reduced to 1% of its original thickness by cold rolling without any intermediate annealing. Bright, lustrous vanadium foil having a smooth finish and a thickness of 2.5 mils was obtained from this regulus by a multi-stage reduction. efiected by a plurality of passes between cold rolls. It may therefore be appreciated that the vanadium metal obtained in accordance with applicants invention is extremely ductile.

In order to obtain ductile vanadium in accordance with the process illustrated in the above example it is highly important to use very pure V205. The nitrogen contact of the V205 should be less than 0.03% to obtain ductile vanadium.

It is not suflicient in itself to specify the use of chemically pure'V205 as commercially supplied in order to produce ductile metal. It has been found that V205 with a residual nitrogen content greater than 0.03% by weight reduces diffusion plug of stainless steel wool is inserted,

the V205 powder is charged into the tube, and a second stainless steel wool plug is inserted. Oxygen gas is bubbled through, water using a porous plate to insure the formation of many wet bubbles. The wet oxygen is streamed through the bed of V205 in the tube for a period ranging from a minimum of two hours to eight een hours at a'temperature of 400 0.; a longer period might be used but is not necessary.

This process may supplement the process in which chemically pure V205 is produced by calcining ammonium metavanadate (NI-I4V03) with an excess of oxygen. Applicants have found that wet oxygen must be used as the final step in the calcining process and that the water present in the oxygen stream aids in breaking down nitrogen compounds formed in the calcining in order to oxidize these compounds to V205. Applicants have also found that the use of dry oxygen is not sufiicient to yield V205 which can reproducibly yield ductile vanadium.

It is important that the reaction mixture,

contain at least 0.05 mol of iodine per mol of V205. Usually the amount of iodine employed varies from about 0.2 mol to about 0.4 mol per mol of V205. The amount of metallic vanadium collected in the regulus appears to increase slightly as increasing proportions of iodine are employed in the reaction mixture. The reaction between the calcium and iodine serves to heat up the reaction mixture in the bomb to a sufficiently high temperature to initiate the reduction of the V205 by the calcium. The addition of iodine to the reaction mixture serves to smooth out the main reduction reaction which is not under control when no iodine is used and also has a small efiect in lowering the melting point of the slag produced in the reaction. The

reaction between V205 and calcium is highly exothermic so that once it has been started it readily goes to completion.

It is important that at least 40%, and preferably from about to about 100% more calcium than is stoichiometrically needed to react with the V205 and iodine in the reaction mixture be initially present in the reaction mixture. The excess calcium serves to flux the calcium oxide produced in the reaction. In addition, the excess calcium hasa gettering effect on any nitrogen remaining in the'bom'b after the precautions described above have been taken to keep nitrogen as low as possible. Applicants avoid the use of calcium chloride as a flux. If V205 containing more than the desired residual nitrogen content is employed, it has been found that the ductility of the vanadium obtained improves as increasing amounts of excess calcium are used. The amount of metallic vanadium ob-- tained in the regulus appears to be somewhat greater when about 50% excess of calcium is employed than when about 100% excess of calcium is used.

It is important to purge the bomb of its air atmosphere which would be detrimental in furnishing nitrogen. Accordingly the bomb is evacuated and flushed with argon or some other nitrogen free inert gas such as neon or helium.

The reaction mixture used in this invention initially consists of vanadium pentoxide, calcium and iodine. The particle size of the V205 used has been a -l00 mesh +325 mesh powder. The calcium normally used has been a -l0 mesh +50 mesh coarse powder. Reductions have also been made using A; inch granules of calcium, but when these granules are used the amount of vanadium collected in the regulus decreases slightly. Iodine is used as resublimed crystals which disperse by volatilization during the early stages of heating. After the reaction has gone to completion the contents of the reaction bomb consist of calcium oxide, calcium iodide, free calcium and free vanadium.

Magnesium may not be used in place of calcium in this invention since magnesium is only effective to reduce V205 to V203.

This invention provides a commercially feasible process for manufacturing massive bodies of ductile vanadium in contrast to the laboratory processes of making small particles of metallic vanadium, which were known to the prior art.

Resort may be had to such modifications and variations as conform to the spirit of the invention and come within the scope of the appended claims.

We claim:

1. A process for obtaining a massive body of ductile vanadium which comprises forming a reaction mixture consisting of vanadium pentoxide, from 0.05 mol to 0.4 mol of iodine per mol of vanadium pentoxide, and at least 40% more metallic calcium than is stoichiometrically needed to react with said vanadium pentoxide and iodine, charging said reaction mixture to a bomb, heating the bomb up to the reaction temperature, and then after the reaction is over separating the massive body of ductile vanadiam thereby obtained from the slag produced in the reaction.

2.'A process for obtaining a massive body of ductilev vanadium which comprises forming a reaction mixture consisting of vanadium pentoxide containing less than 0.03% of residual nitrogen, from 0.05 mol to 0.4 mol of iodine per mol of vanadium pentoxide, and from about 50% to about 100% more metallic calcium than is stoichiometrically needed to, react with said vanadium pentoxide and iodine, charging said reaction mixture to a bomb, heating the bomb up to the reaction temperature, and then after the reaction is over separating the massive body of ductile vanadium thereby obtained from the slag produced in the reaction.

3. A process for obtaining a massive body of ductile vanadium which comprises forming a reaction mixture consisting of vanadium pentoxide, the residual nitrogen content of which has been reduced to less than 0.03% by heat treatment of the pentoxide with wet oxygen at 400 0., from about 0.2 mol to about 0.4 mol of iodine per mol of vanadium pentoxide, and from about 50% to about 100% more metallic calcium than is stoichiometrically needed to react with said. vanadium pentoxide and iodine, charging said reaction mixture to a bomb, purging the UNITED STATES PATENTS atmospheric gases contained in said bomb and Number Name Date replacing them with a nitrogen free inert gas, 1,533 505 Lubowsky Apr. 14 1925 heating the bomb up to the reaction tempera- 1 8143719 Marden et a1. July 1931 ture, and then after the reaction has subsided 5 1:814 720 Marden et a1. July 1931 and the reaction mass has cooled separating the 2 446062 Rentschler at July 1948 massive body of ductile vanadium thereby obtained from the slag produced in the reaction. OTHER REFERENCES if? CHNIE' 10 Comprehensive Treatise on Inorganic and JOHN E. GRAY Theoretical Chemistry, by Mellor, v01. 9, page 725, published by Longmans, Green 8: C0., REFERENCES CITED New rk, 1929.

The following references are of record in the file of this patent: 15 

1. A PROCESS FOR OBTAINING A MASSIVE BODY OF DUCTILE VANADIUM WHICH COMPRISES FORMING A REACTION MIXTURE CONSISTING OF VANADIUM PENTOXIDE, FROM 0.05 MOL TO 0.4 MOL OF IODINE PER MOL OF VANADIUM PENTOXIDE, AND AT LEAST 40% MORE METALLIC CALCIUM THAN IS STOICHIOMETRICALLY NEEDED TO REACT WITH SAID VANADIUM PENTOXIDE AND IODINE, CHARGING SAID REACTION MIXTURE TO A BOMB, HEATING THE BOMB UP TO THE REACTION TEMPERATURE, AND THEN AFTER THE REACTION IS OVER SEPARATING TEH MASSIVE BODY OF DUCTILE VANADIUM THEREBY OBTAINED FROM THE SLAG PRODUCED IN THE REACTION. 